uva 10246 Asterix and Obelix(最短路问题拓展 dijkstra)

题意:给定一个图,每个点都有一个代价,,每个边也都有一个代价,现在给定两个点,让求从一个点到另一个点的最小代价。 最小代价 = 经过的边的代价和 + 经过的最大代价的哪一个点的代价

解题思路:

一共只有80个点 所以可以枚举每一个点,然后把当前点的代价作为最小代价,代价高于这个点的点就不走(即该条边再找最短路的过程中不使用),然后把这个点作为起点,dijkstra求该点到其他点的最短路。

然后处理两点之间的最短路+当前点的代价 = 两点之间的最小代价;

在以后枚举每一个点的过程中,每两点之间的最小代价都有可能被更新~

code:

#include<cstdio>#include<cstring>#include<algorithm>#include<queue>#include<vector>using namespace std;const int MAXNODE = 200;const int MAXEDGE = 3000;typedef int Type;const Type INF = 0x3f3f3f3f;struct Edge {int u, v;Type dist;Edge() {}Edge(int u, int v, Type dist) {this->u = u;this->v = v;this->dist = dist;}};struct HeapNode {Type d;int u;HeapNode() {}HeapNode(Type d, int u) {this->d = d;this->u = u;}bool operator < (const HeapNode& c) const {return d > c.d;}};int n, m, q, cost[MAXNODE], ans[MAXNODE][MAXNODE];struct Dijkstra {int n, m;Edge edges[MAXEDGE];int first[MAXNODE];int next[MAXEDGE];bool done[MAXNODE];Type d[MAXNODE];int p[MAXNODE];void init(int n) {this->n = n;memset(first, -1, sizeof(first));m = 0;}void add_Edge(int u, int v, Type dist) {edges[m] = Edge(u, v, dist);next[m] = first[u];first[u] = m++;}void dijkstra(int s) {priority_queue<HeapNode> Q;for (int i = 0; i < n; i++) d[i] = INF;d[s] = 0;p[s] = -1;memset(done, false, sizeof(done));Q.push(HeapNode(0, s));while (!Q.empty()) {HeapNode x = Q.top(); Q.pop();int u = x.u;if (done[u]) continue;done[u] = true;for (int i = first[u]; i != -1; i = next[i]) {Edge& e = edges[i];if (cost[e.v] > cost[s]) continue;if (d[e.v] > d[u] + e.dist) {d[e.v] = d[u] + e.dist;p[e.v] = i;Q.push(HeapNode(d[e.v], e.v));}}}///当固定起点和固定了最大点代价时,更新两点之间的最小代价for (int i = 0; i < n; i++) {for (int j = 0; j < n; j++) {ans[i][j] = min(ans[i][j], d[i] + d[j] + cost[s]);}}}} gao;void init(){for(int i = 0; i < n; i++) {scanf("%d",&cost[i]);}int u,v,w;for(int i = 0; i < m; i++){scanf("%d%d%d",&u,&v,&w);u–;v–;gao.add_Edge(u,v,w);gao.add_Edge(v,u,w);}}void solve(){memset(ans,INF,sizeof(ans));///枚举每一个点作为最大代价点for(int i = 0; i < n; i++){gao.dijkstra(i);}int s,t;// printf("q = %d\n",q);for(int i = 0; i < q; i++){scanf("%d%d",&s,&t);s–;t–;if(ans[s][t] == INF) printf("-1\n");///说明两点之间并不存在路径else printf("%d\n",ans[s][t]);}}int main(){int cas = 0;while(scanf("%d%d%d",&n,&m,&q)){if(!n&&!m&&!q) break;if(cas) printf("\n");gao.init(n);init();printf("Case #%d\n",++cas);solve();}return 0;}

到尽头,也许快乐,或有时孤独,如果心在远方,

uva 10246 Asterix and Obelix(最短路问题拓展 dijkstra)

相关文章:

你感兴趣的文章:

标签云: